Need help with Kohler shower plumbing design

[TowerPower]

I’m planning to swap out an 8300 Rite-temp valve that is currently roughed in from previous plumber. It was set up for shower head only with bottom port capped off. (Was told would not work for what I want to do)
Have a K-11748-KS main valve with tub diverter and service stops - shower stall only, BUT wanting to have a tub spout for “toe tester” as well as bucket filler if ever desired. Also wanting to run a shower head, handshower and body spray. I have the 728 transfer valve I was planning to use for the head, handshower and body spray as well as a volume control valve to control shower head output and was hoping I could use the diverter button/bottom port of the K-11748-KSfor my tub spout. But after reading some of the expert opinions here; I’m doubting my way of thinking… is it better to invert the K-11748-KS so I have more output to my 728 transfer valve or does it really matter?
Please advise this lost puppy on the best way to proceed.


Anyone have any thoughts regarding this… need help before I make a major mistake lol.

By the way, tub spout is primarily for testing the water before turning on the shower head so lower volume there is ok. So I guess my main question is should I flip the main K-11748-KS valve upside down to increase flow to 728 3 way transfer valve and if so do I need to do anything else besides flipping the cartridge too? Looking at the K-11748-KS valve i do see that the bottom port does have a slightly larger diameter discharge hole than the the “top” hole. Also would 3/4” pex “expansion” be ok for tub spout or is copper/brass mandatory?
I’m now wondering if doing things this way will create a problem with water flow diverting down to the tub spout if I use volume controls on shower head or hand sprayer… would that back pressure be allowed to exit at tub spout or how does that work?? Should I leave the original Rite-temp 8300 valve in if the K-11748-KS is not adequate? Is there a better valve for what I’m trying to do or is 4 functions in a shower just asking for too much?? (OCD at its finest lol)

https://www.us.kohler.com/webassets/kpna/catalog/pdf/en/K-2972-KS_spec_US-CA_Kohler_en.pdf

https://www.kohler.com/en/search?keyword=master+shower

 

[TowerPower]

Would a “twin ell” help me as shown in this Kohler valve depiction? I’m not sure of the dynamics of how something like this helps, it seems to be required…

https://www.us.kohler.com/webassets/kpna/catalog/pdf/en/085755-2.pdf

 

[Sponsor]

 

[Jeff H Young]

Looks wrong to me , funny papers show twin ell and volume control on bottom If you can't make sense out of them I'd recommend contacting Kohler also ask about 3/4 PEX to spout

 

[John Gayewski]

It looks to me like the twin El is the only way to guarantee four outlets to work properly. I wouldn't diverge from the manufacturer instructions very much unless I was very familiar with the dynamics of a particular valve, which in this case, I'm not.

 

[Tuttles Revenge]

It seems like the valve you want is the K-11748-KS

It defaults to the tub spout position. Diverts up to the shower position which you would add a transfer valve K-737 to each of the 3 other functions. No volume control / ON-OFF on your shower head or you risk mixing hot cold through your entire house.

 

[TowerPower]

It seems like the valve you want is the K-11748-KS

It defaults to the tub spout position. Diverts up to the shower position which you would add a transfer valve K-737 to each of the 3 other functions. No volume control / ON-OFF on your shower head or you risk mixing hot cold through your entire house.

View attachment 89045

Thanks for your reply! Correction on my original post.. I do have the K-11748-KS valve currently.. I’m not sure where I came up with 304 number… I will edit my post.
Also curious why/how having a volume control or on/off controller on the shower head would cause any problems mixing water throughout the house… All of my past showerheads have had volume controls on them and I’ve never noticed an issue.

https://www.us.kohler.com/webassets/kpna/catalog/pdf/en/1128093-2.pdf

 

[Tuttles Revenge]

Thanks for your reply! Correction on my original post.. I do have the K-11748-KS valve currently.. I’m not sure where I came up with 304 number… I will edit my post.
Also curious why/how having a volume control or on/off controller on the shower head would cause any problems mixing water throughout the house… All of my past showerheads have had volume controls on them and I’ve never noticed an issue.

Pressure balance valves are not intended to have on / off functions after the mixer valve. When the mixer is turned on and the output is turned off that leaves the valve open. When another faucet in the home is opened you have a cross connection that can send that mixed water to that open faucet.

However... now that I'm thinking about it. New Kohler valves with their integral stops have check valves built in. I don't think any of the other valves do tho.

 

[TowerPower]

Pressure balance valves are not intended to have on / off functions after the mixer valve. When the mixer is turned on and the output is turned off that leaves the valve open. When another faucet in the home is opened you have a cross connection that can send that mixed water to that open faucet.

However... now that I'm thinking about it. New Kohler valves with their integral stops have check valves built in. I don't think any of the other valves do tho.

So should I invert/flip my main valve so the tub port with the larger diameter output hole is facing towards the transfer valve to increase flow… in that situation, would the tub spout output be engaged by pushing in the diverter button? I’m trying to come up with a scenario where the tub spout/toe tester will have the water coming out first when turning on the valve so I can make sure the temperature is right before hitting the showerhead, body spray or hand shower.
Also, does the “twin ell” need to be use in either scenario to prevent back flow in some way??

 

[John Gayewski]

I don't think I'd flip it. I guess it depends on the design of the valve but the larger volume may be needed to keep the diverter closed.

 

[TowerPower]

It looks to me like the twin El is the only way to guarantee four outlets to work properly. I wouldn't diverge from the manufacturer instructions very much unless I was very familiar with the dynamics of a particular valve, which in this case, I'm not.

So I was mistaken with the 304 valve.. it’s actually the k-11748-ks valve. Dose that make a difference in your statement? Do you know this valves dynamics?

 

[Tuttles Revenge]

OK.. I take that back.

The K-8304-KS has integral stops with built in check valves. But I don't think the K-11748-KS stops have check valves in which case no On/Off valves can be used after the mixer.

The above Illustration with the use of the volume control and the twin ell are for a Thermostatic valve. Which requires the use of a volume control(s) and why a twin ell is used since the thermostatic can't divert on its own. That system doesn't have a Default to Tub setting like the pressure balance system does. Water comes out of whichever port is left in the open posistion.

I've never heard of any manufacturer recommending flipping a valve over for increased flow. I wouldn't recommend it either. I would never install something like that without bench testing it prior. once its behind tile its pretty much a done deal. I doubt it would actually increase flow to any noticeable amount regardless.


All that being said your original diagram works if the volume control is not installed or ever turned to off while the shower valve is left on. Shower outlets being limited to 2.5 or 1.8 and the diverter sending full flow to 1 or partial flow to 2 functions will always be less volume than the valve can supply. I don't think you need to try anything fancy with the mixer.

 

[TowerPower]

OK.. I take that back.

The K-8304-KS has integral stops with built in check valves. But I don't think the K-11748-KS stops have check valves in which case no On/Off valves can be used after the mixer.

The above Illustration with the use of the volume control and the twin ell are for a Thermostatic valve. Which requires the use of a volume control(s) and why a twin ell is used since the thermostatic can't divert on its own. That system doesn't have a Default to Tub setting like the pressure balance system does. Water comes out of whichever port is left in the open position.

I've never heard of any manufacturer recommending flipping a valve over for increased flow. I wouldn't recommend it either. I would never install something like that without bench testing it prior. once its behind tile its pretty much a done deal. I doubt it would actually increase flow to any noticeable amount regardless.


All that being said your original diagram works if the volume control is not installed or ever turned to off while the shower valve is left on. Shower outlets being limited to 2.5 or 1.8 and the diverter sending full flow to 1 or partial flow to 2 functions will always be less volume than the valve can supply. I don't think you need to try anything fancy with the mixer.

Thank you so much for that information!
Since I have 1/2” PEX supplying the valve (converted from 3/4” PEX about 4 feet away inside sheetrocked wall) I was a little worried about GPM/ volume to my outputs. I opted for 3/4” PEX a expansion fittings going from the 1/2” output of the valve into the 3/4” input of the transfer valve thinking it can’t hurt and might actually help… I also made a 3/4” pressure balance loop for the body sprays per a previous post I read here. I supplied that loop with 3/4” PEX from the transfer valve.

 

[Tuttles Revenge]

Test your body spray system.. Looks good with the center cross tube, but body sprays are always a big disappointment for customers when they dont feel like their skin is being peeled off.

 

[TowerPower]

Test your body spray system.. Looks good with the center cross tube, but body sprays are always a big disappointment for customers when they don't feel like their skin is being peeled off.

Think I will be ok using 3/4 PEX a expansion from bottom port to tub spout or would you recommend copper or brass fittings? The 3/4” PEX using the larger ID expansion hose seems almost as large as 1/2” copper to me.. does it make that much of a difference in back pressure?

 

[John Gayewski]

Think I will be ok using 3/4 PEX a expansion from bottom port to tub spout or would you recommend copper or brass fittings? The 3/4” PEX using the larger ID expansion hose seems almost as large as 1/2” copper to me.. does it make that much of a difference in back pressure?

Use copper for the tub spout.

 

[TowerPower]

I had originally purchased the

Thermostatic cartridge​

K-28305-NA for use in the K-11748-KS valve that I’m considering replacement of for the tub spout option which isn’t sounding great right now with either valves… I’m seeing the GPM’s of the 28305 cartridge at 9 which is almost double of the 8304 with built in diverter.
Is the 3 way diverter after the thermostatic cartridge acceptable/reccomended? Seems like that might be the way to go and just lose my toe tester/tub spout… it’s very confusing to me. I had originally planned to use the original valve/cartridge with the transfer valve above it sending mixed water off to shower head, handsprayer and/or body spray and was going to use a volume control off the bottom (currently capped) port to the tub spout, but the cartridge info say “Do not install a shut-off device on either outlet of this valve. The device may create crossflow at the valve, affecting the water temperature.”

Kohler valve instructions

Thermostatic cartridge information

• 9 gpm (34 l/min) maximum flow rate at 45 psi. •
• Requires trim and any K-8300 valve body to complete installation (sold separately).

 

[Terry]

I don't see a reason for a toe tester tub spout. It's already getting pretty complicated.

 

[TowerPower]

I don't see a reason for a toe tester tub spout. It's already getting pretty complicated.

I totally get it.. problem is I’ve already owned the Kohler trim kit and tub spout (which were not cheap) for some time now.
I can return the newer pressure balance valve K-11748-KS (Amazon) but I’m stuck with the tub spout, handshower, body sprays, the 8300 valve and thermostatic cartridge and the trim kit with diverter hole. Was hoping to be able to use everything somehow…

I’m guessing the best way to continue is with the existing (already roughed in) 8300 valve and thermostatic cartridge due to its higher 9 gpm flow rating. Using a 2.5 gpm shower head, 2.5 gpm handshower, and two 2.5 gpm body sprays would definitely would be too much for the shower/upper port outlet of the 5 gpm K-11748-KS valve with tub diverter output. I’m going through the 728 3-way diverter valve and would like to be able to use dual function with shower head/body sprays or shower head/handshower if desired without losing too much flow/volume.
Can the thermostatic cartridge/valve be used with only the one transfer valve or does it require more than one? Can it be used with a volume control for the shower head. (The cartridge does have built in check valves I believe)

 

[Jeff H Young]

Like I said call Kohler is my advice draw it up and get their blessing

 

[Terry]

Like I said call Kohler is my advice draw it up and get their blessing

You can ask Kohler, it's going to cost you though.